The aim of this project is to study adaptive mechanisms and higher level interactions in the visual system by building on established knowledge about the early mechanisms of human color vision. Experimental and theoretical work is proposed in five different categories: (1) The interaction between opponent color signal changes as an adaptation to correlated stimulation. A dynamic model of associative adaptation will be based on the results of experiments that measure the magnitude and rate of change in interactions as a function of the degree of correlated stimulation. (2) The adaptive behavior of the two opponent color systems can be explained in terms of pre- and post-opponent static and adaptive mechanisms. The location and temporal properties of these mechanisms will be studied by manipulating colors along theoretically defined lines at higher intensities than studied previously. (3) The visual system includes mechanisms that signal the direction of change in colors. Discrimination thresholds between pairs of color modulations around an equiluminant color circle at a number of different rates will be used to study the manner in which color and temporal signals are combined. (4) The appearance of test colors is influenced by surrounding colors. Experiments on the induced effect of circularly symmetric and tangentially varying sinusoidal surrounds will be used to build a model of the lateral interactions within color mechanisms. This model will incorporate weighted spatial integration, time-lags, and spatially nonlinear interactions. (5) In visual memory, chromatic information is more useful than luminance information. Experiments will identify the type of information that is remembered best by each color mechanism and factors that can interfere with the storage of this information. It is expected that the visual mechanisms identified in this project by psychophysical experiments will provide insights into neural functions and a guide for electrophysiological studies.